The present application claims priority to Japanese Application No. JP 11-279,789 filed Sep. 30, 1999, which application is incorporated herein by reference to the extent permitted by law.
1. Field of the Invention
The present invention relates to a solid electrolyte cell including a rolled electrode body having a strip positive electrode and a strip negative electrode which are layered via a solid electrolyte layer and rolled in the longitudinal direction.
2. Description of the Prior Arts
Recently, electronic apparatuses are reducing their sizes so as to be portable and improving their performances. In response to this, the cell as an energy storage source should also be reduced in size and have a higher capacity. A special attention is paid on a lithium-ion secondary cell having a high operation voltage and a high energy density. The current lithium-ion secondary cell uses a non-aqueous electrolytic solution, which causes a problem of leak of the electrolytic solution. In order to solve this problem, a study has been made on cells using a gel electrolyte and a solid electrolyte. These cells have no problem of leak of the electrolyte and have an advantage that the cells can be made thin and are flexible and now widely applied to small-size portable apparatuses.
A conventional thin-type cell has been produced as follows. A strip positive electrode, a separator, a strip negative electrode are layered into a layered body, which is rolled into a rolled electrode body. After this, an electrode terminal is attached to the positive electrode and the negative electrode and the rolled electrode body is wrapped in a plastic film laminate member by heat sealing at several position of the laminate member or vacuum sealing, so as to obtain a thin-type cell.
However, in the conventional solid electrolyte cell, when the cell is pushed by an external pressure, short circuit may be caused between the positive electrode and the negative electrode in the cell, which in turn causes a heat and smoke, deteriorating the entire cell. Moreover, the existing cell uses a strip electrode having no exposure of electrode collector and when this electrode is rolled, the outermost circumference also has the electrode active material layer which is not used, thus causing a loss in volume energy density.
It is therefore an object of the present invention to provide a solid electrolyte cell capable of suppressing a damage caused when the cell is pushed and broken.
The solid electrolyte cell according to the present invention includes a rolled electrode body consisting of a positive electrode having a strip electrode collector whose both sides are coated with a positive electrode active material layer and a negative electrode having a strip negative electrode collector whose both sides are coated with a negative electrode active material layer. The positive electrode and the negative electrode are layered via a solid electrolyte layer and rolled in the longitudinal direction. The rolled electrodes have a collector one-side exposed portion at their one end in the longitudinal direction to be positioned at the outermost circumference and the collector one-side exposed portion covers the outer circumference of the rolled electrode body by one turn one more.
In the solid electrolyte cell having the aforementioned configuration according to the present invention, one end of the electrodes to be positioned at the outermost circumference has a collector one-side exposed portion, which covers the outer circumference of the rolled electrode body by one turn or more. Accordingly, even if the cell is pushed to be collapsed and shot-circuit is caused between the positive electrode and the negative electrode, at the early stage, the collector exposed portion diffuses the heat caused by the short-circuit, causing almost no affect to the electrode active material layer and not damaging the entire cell.